Aluminum—1. A review of resistive mechanisms in aluminum

The bulk of the article is concerned with a critical discussion of inductive, electrodeless techniques that enable the resistivity of a metal to be investigated, especially by the use of massive samples, with or without the presence of a strong magnetic field. The principal methods are the following: modification of the inductance of a coil by a metal core, eddy current decay, `hard' helicons in a rigidly mounted sample, `soft' helicons in an elastically mounted sample and torque on a sphere turning in a steady transverse field. The theory underlying the methods is expounded, but greatest attention is paid to the variety of disturbing effects that can introduce significant errors, and to the refinements of technique and analysis needed to minimize them. Although the literature is reviewed in some detail, much of the material is new. In an introduction the problems of conventional measurements, by four-terminal methods, in the presence of strong magnetic fields are outlined, particularly the `current-jetting' effects that can cause disastrous errors. This review was completed in January 1972.

http://iopscience.iop.org/article/10.1088/0034-4885/35/2/304/pdf

Electrodeless methods for conductivity measurement in metals

Study of the Transverse Magnetoresistance of Polycrystalline Potassium.

Low-field Hall coefficient R and transverse magnetoresistance Delta rho / rho 0 were measured in Al single crystals. A definite defect structure (statistically distributed Frenkel pairs) was created in the specimens by low-temperature electron irradiation. This defect structure could then be changed in a controlled way by annealing at different temperatures. Eliminating the influence of defect concentration with the aid of the Kohler representation thus allowed the dependence of R and Delta rho / rho 0 on the defect structure to be investigated. Various effects of the Fermi surface geometry and of the scattering mechanism on R and Delta rho / rho 0 are discussed on the basis of simple equations for the low-field Hall coefficient and magnetoresistance.

Influence of Fermi surface and defect structure on the lowfield galvanomagnetic properties of Al

The influence of electron scattering on the high-field galvanomagnetic properties was investigated by measuring transverse magnetoresistance and Hall effect in an Al single crystal with different defect structures. A systematic variation of the number and the kind of defects was achieved by low-temperature electron irradiation and subsequent annealing at different temperatures. Obeying Kohler's rule, the high-field magnetoresistance does not change with defect concentration. However, it depends sensitively on the defect configuration. On the other hand the anisotropy of the magnetoresistance is observed to be independent of the defect configuration. That means the anisotropy is solely determined by the anisotropy of the Fermi surface. New evidence for explaining the linear high-field magnetoresistance by magnetic breakdown was found and orientation-dependent geometry effects on the transverse magnetoresistance are discussed.

High-field magnetoresistance and hall effect in aluminium single crystals. Influence of Fermi surface and defect structure

The transverse magnetoresistance, pxx, of an aluminium single crystal has been measured at 4·2°K in fields in the [001] direction up to 60 koe. Above 20 koe it is observed to undergo large oscillations, periodic in reciprocal field, with a frequency of 4·59 × 105 oe. The oscillations are superimposed on a background whose slope increases with field. The Hall component of resistance, pyx, is found to be proportional to field and not to oscillate, and the longitudinal magnetoresistance, pzz, does not saturate and undergoes small oscillations. The cause of the behaviour of pxx and pyx is shown to be magnetic breakdown, which allows holes to change from one orbit to another in an adjacent Brillouin zone using a third zone part of the Fermi surface as a bridge. This mechanism alters the effective paths of the electrons and leads to a higher resistance than would obtain if only simply closed orbits were possible. The resistance oscillations are a consequence of the field dependence of the probability o...

R. J. Balcombe

Papers

The influence of magnetic breakdown on the high field magnetoresistance of aluminium